This invention relates to an outboard motor and more particularly to an improved lubricating and mounting system for a four-cycle internal combustion engine particularly adapted for use in such a motor.
Outboard motors generally use two-cycle engines as their means for propulsion. The reason that two-cycle engines have been prominently used in connection with outboard motors is the difficulty in providing a compact and yet serviceable four-cycle engine for such an application. One of the large problems in connection with employing four-cycle engines for use in outboard motors is the difficulty in providing a crankcase or oil sump of sufficient capacity while maintaining a compact arrangement. Normally the cylinders of the engine lie on a horizontal plane and the crankshaft extends vertically. This means that the sump or oil pan must be disposed externally of the engine. The engine is normally positioned above the driveshaft housing and is contained within a cowling. If a separate oil pan is disposed beneath the cylinder block or crankcase and within the upper housing or power head above the driveshaft housing, the height of the engine becomes unduly cumbersome. In addition, the large weight of the engine and the oil pan are so elevated as to make tilting of the engine as is required in an outboard motor application difficult. In addition, this high positioning of the engine and oil pan gives rise to mounting strength problems and also makes serviceability of the engine difficult.
It is, therefore, a principal object of this invention to provide an improved lubricating system for a four-cycle internal combustion engine that lends itself to application in an outboard motor.
It is another object of this invention to provide a four-cycle lubricating system for an outboard motor wherein the oil pan and engine may be mounted independently of each other and the oil pan will not encroach into the power head casing.
When a four-cycle engine is employed as a power unit for an outboard motor, the oil pan also must be designed in such a way as to permit tilting of the engine from its normal running position to its tilted up position without having oil leakage. A particular problem in this regard may be presented if the oil is permitted to leak back into the cylinder head when the engine is tilted up.
It is, therefore, a further object of this invention to provide an improved oil pan arrangement for a four-cycle internal combustion engine in an outboard motor in which oil leakage is prevented even when the engine is tilted up.
In addition to the difficulties in positioning the oil pan for a four-cycle internal combustion engine used as an outboard motor, the system should provide good lubrication of all components. This lubrication problem is particularly acute in an outboard motor application in view of the fact that the crankshaft and camshaft both rotate about vertically disposed axes. It is desirable to maintain the oil lines for the engine to a minimum so as to reduce cost and avoid problems that may be encountered when a large number of oil lines are used. However, the lubrication system should insure adequate lubrication of all of the bearings, considering the particular difficulty that the shafts rotate about vertical axes.
It is, therefore, a still further object of this invention to provide an improved lubricating system for a four-cycle engine when the engine is operated with its crankshaft and camshaft extending vertically.
It is a further object of this invention to provide an engine lubricating system that minimizes the number of oil passages without sacrificing lubrication.